Server restart management via stability time

ABSTRACT

A computer-implemented method for monitoring server stability based on a stability time specification of a server includes specifying a stability time for the server, wherein the stability time is defined as a time between a starting state of the server and a stability point of the server. The server activity is monitored by an availability manager to determine an availability status of the server. Responsive to the server activity progressing to the stability point within the stability time, an embodiment determines that the server is stable. Responsive to the server activity failing to progress to the stability point within the stability time, an embodiment determines that the server is unreliable.

DOMESTIC PRIORITY

This application is a continuation of U.S. patent application Ser. No.13/747,887, filed Jan. 23, 2013, the disclosure of which is incorporatedby reference herein in its entirety.

BACKGROUND

The present invention relates to server stability, and morespecifically, to monitoring server stability based on a stability timespecification of the server.

In the contemporary art, a virtual server is a virtual machine hosted bya hypervisor. A single server machine may host many virtual servers,where each virtual server represents a share of computer resources, suchas central processing unit (CPU), memory, and storage resources, andhosts a separate operating system (OS) image. The OS image executesmiddleware and business applications, and can be operated and rebootedindependently from other virtual servers.

Typically, a collection of managed virtual servers, such as a WorkloadResource Group (WRG), include virtual servers of differentarchitectures, all working together to execute a business workload. TheOS image on each virtual server may provide some value-addedcontribution to the overall business workload. Contemporary computingenvironments detect the failure of a virtual server and restart thevirtual server “in place.” In other words, the failing virtual server isterminated and restarted, often on the same system, virtual server, orin the same virtual machine. A set of redundant virtual servers istypically defined to process the same business functions as the failingvirtual server and take over in case of restart or failure.

SUMMARY

According to an embodiment, a computer-implemented method is providedfor monitoring server stability based on a stability time specificationof a server. An embodiment specifies a stability time for the server,wherein the stability time is defined as a time between a starting stateof the server and a stability point of the server. The server activityis monitored by an availability manager to determine an availabilitystatus of the server. Responsive to the server activity progressing tothe stability point within the stability time, an embodiment determinesthat the server is stable. Responsive to the server activity failing toprogress to the stability point within the stability time, an embodimentdetermines that the server is unreliable.

According to another embodiment, a computer program product is providedfor executing a method for monitoring server stability based on astability time specification of a server. An embodiment specifies astability time for the server, wherein the stability time is defined asa time between a starting state of the server and a stability point ofthe server. The server activity is monitored by an availability managerto determine an availability status of the server. Responsive to theserver activity progressing to the stability point within the stabilitytime, an embodiment determines that the server is stable. Responsive tothe server activity failing to progress to the stability point withinthe stability time, an embodiment determines that the server isunreliable.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 depicts a cloud computing node according to an embodiment of thepresent invention;

FIG. 2 depicts a cloud computing environment according to an embodimentof the present invention;

FIG. 3 depicts abstraction model layers according to an embodiment ofthe present invention;

FIG. 4 depicts an availability manager of a workload resource group(WRG) according to an embodiment;

FIG. 5 depicts a flow diagram of a monitoring operation for determiningthe stability of a server based on a stability time specification of theserver according to an embodiment; and

FIG. 6 depicts a timeline demonstrating the relation between a stabilitytime, an availability status, and a lifecycle of a server according toan embodiment.

DETAILED DESCRIPTION

Embodiments disclosed herein determine the stability and availabilitystatus of a server by monitoring the stability time specification of theserver. According to embodiments, the stability time is specified forthe server. The stability time is defined as the time between a startingstate of the server and the stability point of the server. Anavailability manager of embodiments monitors the server activity todetermine an availability status of the server. In response to theserver activity progressing to the stability point within the stabilitytime, embodiments determine that the monitored server is stable. Inresponse to the server activity failing to progress to the stabilitypoint within the stability time, embodiments determine that the serveris unreliable, without knowledge of the specific OS or other processingrunning in the virtual server.

Contemporary computing environments typically detect the failure of aprocess or server and restart that process “in place”. In other words,the failing server is terminated and restarted, often on the samesystem, server, or in the same virtual machine. However, it is possiblethat restarting the server would result in the server failing again, ortaking too long to become truly “available” (i.e., ready to processuseful work). Restarting the server too soon could cause the server to(1) hang, such that the server's start or restart does not make progressto a full function ready state, (2) fail immediately and subsequentlyrestart, which if unconstrained would result in restart “thrashing”, or(3) consistently fail after a period of useful productive work.

Contemporary computing environments typically determine whether a serveris stable by monitoring for direct execution errors or related errorsymptoms exhibited by the server environment. The contemporary approachfocuses primarily on rich levels of error detection in the OS and otherhosted processing, and requires detailed observations of the monitoredservers. While a wealth of architecture and OS specific error data canbe collected, it may not be available, especially if the hosted virtualservers and OS images are not instrumented to provide such information.

Embodiments disclosed herein provide a stability time as the time toreach a stability point in the initialization of the virtual server. Anavailability manager observes the execution of servers among acollection of different server architectures and determines serverstability by monitoring whether the server remains active long enough tobe considered reliable. When the server reaches the stability point, theserver is available for use in business workloads and is no longerconsidered a potentially unreliable part of the workload.

It is understood in advance that although this invention includes adetailed description on cloud computing, implementation of the teachingsrecited herein are not limited to a cloud computing environment. Rather,embodiments of the invention are capable of being implemented inconjunction with any other type of computing environment now known orlater developed.

Cloud computing is a model of service delivery for enabling convenient,on-demand network access to a shared pool of configurable computingresources (e.g., networks, network bandwidth, servers, processing,memory, storage, applications, virtual machines, and services) that canbe rapidly provisioned and released with minimal management effort orinteraction with a provider of the service. This cloud model may includeat least five characteristics, at least three service models, and atleast four deployment models.

Characteristics are as follows:

On-Demand Self-Service: a cloud consumer can unilaterally provisioncomputing capabilities, such as server time and network storage, asneeded automatically without requiring human interaction with theservice's provider.

Broad Network Access: capabilities are available over a network andaccessed through standard mechanisms that promote use by heterogeneousthin or thick client platforms (e.g., mobile phones, laptops, and PDAs).

Resource Pooling: the provider's computing resources are pooled to servemultiple consumers using a multi-tenant model, with different physicaland virtual resources dynamically assigned and reassigned according todemand. There is a sense of location independence in that the consumergenerally has no control or knowledge over the exact location of theprovided resources but may be able to specify location at a higher levelof abstraction (e.g., country, state, or datacenter).

Rapid Elasticity: capabilities can be rapidly and elasticallyprovisioned, in some cases automatically, to quickly scale out andrapidly released to quickly scale in. To the consumer, the capabilitiesavailable for provisioning often appear to be unlimited and can bepurchased in any quantity at any time.

Measured Service: cloud systems automatically control and optimizeresource use by leveraging a metering capability at some level ofabstraction appropriate to the type of service (e.g., storage,processing, bandwidth, and active user accounts). Resource usage can bemonitored, controlled, and reported providing transparency for both theprovider and consumer of the utilized service.

Service Models are as follows:

Software as a Service (SaaS): the capability provided to the consumer isto use the provider's applications running on a cloud infrastructure.The applications are accessible from various client devices through athin client interface such as a web browser (e.g., web-based e-mail).The consumer does not manage or control the underlying cloudinfrastructure including network, servers, operating systems, storage,or even individual application capabilities, with the possible exceptionof limited user-specific application configuration settings.

Platform as a Service (PaaS): the capability provided to the consumer isto deploy onto the cloud infrastructure consumer-created or acquiredapplications created using programming languages and tools supported bythe provider. The consumer does not manage or control the underlyingcloud infrastructure including networks, servers, operating systems, orstorage, but has control over the deployed applications and possiblyapplication hosting environment configurations.

Infrastructure as a Service (IaaS): the capability provided to theconsumer is to provision processing, storage, networks, and otherfundamental computing resources where the consumer is able to deploy andrun arbitrary software, which can include operating systems andapplications. The consumer does not manage or control the underlyingcloud infrastructure but has control over operating systems, storage,deployed applications, and possibly limited control of select networkingcomponents (e.g., host firewalls).

Deployment Models are as follows:

Private Cloud: the cloud infrastructure is operated solely for anorganization. It may be managed by the organization or a third party andmay exist on-premises or off-premises.

Community Cloud: the cloud infrastructure is shared by severalorganizations and supports a specific community that has shared concerns(e.g., mission, security requirements, policy, and complianceconsiderations). It may be managed by the organizations or a third partyand may exist on-premises or off-premises.

Public Cloud: the cloud infrastructure is made available to the generalpublic or a large industry group and is owned by an organization sellingcloud services.

Hybrid Cloud: the cloud infrastructure is a composition of two or moreclouds (private, community, or public) that remain unique entities butare bound together by standardized or proprietary technology thatenables data and application portability (e.g., cloud bursting forload-balancing between clouds).

A cloud computing environment is service oriented with a focus onstatelessness, low coupling, modularity, and semantic interoperability.At the heart of cloud computing is an infrastructure comprising anetwork of interconnected nodes.

Referring now to FIG. 1, a block diagram of a cloud computing node forcollectively aggregating digital recordings of an event of an embodimentis shown. Cloud computing node 10 is only one example of a suitablecloud computing node and is not intended to suggest any limitation as tothe scope of use or functionality of embodiments described herein.Regardless, cloud computing node 10 is capable of being implementedand/or performing any of the functionality set forth hereinabove.

In cloud computing node 10 there is a computer system/server 12, whichis operational with numerous other general purpose or special purposecomputing system environments or configurations. Examples of well-knowncomputing systems, environments, and/or configurations that may besuitable for use with computer system/server 12 include, but are notlimited to, personal computer systems, server computer systems, thinclients, thick clients, hand-held or laptop devices, multiprocessorsystems, microprocessor-based systems, set top boxes, programmableconsumer electronics, network PCs, minicomputer systems, mainframecomputer systems, and distributed cloud computing environments thatinclude any of the above systems or devices, and the like.

Computer system/server 12 may be described in the general context ofcomputer system-executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 12 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 1, computer system/server 12 in cloud computing node 10is shown in the form of a general-purpose computing device. Thecomponents of computer system/server 12 may include, but are not limitedto, one or more processors or processing units 16, a system memory 28,and a bus 18 that couples various system components including systemmemory 28 to processor 16.

Bus 18 represents one or more of any of several types of bus structures,including a memory bus or memory controller, a peripheral bus, anaccelerated graphics port, and a processor or local bus using any of avariety of bus architectures. By way of example, and not limitation,such architectures include Industry Standard Architecture (ISA) bus,Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI) bus.

Computer system/server 12 may include a variety of computer systemreadable media. Such media may be any available media that is accessibleby computer system/server 12, and it includes both volatile andnon-volatile media, removable and non-removable media.

System memory 28 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 30 and/or cachememory 32. Computer system/server 12 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 34 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “flash drive”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 18 by one or more datamedia interfaces. As will be further depicted and described below,memory 28 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments.

Program/utility 40, having a set (at least one) of program modules 42,may be stored in memory 28 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. Program modules 42 generally carry out the functions and/ormethodologies of embodiments as described herein.

Computer system/server 12 may also communicate with one or more externaldevices 14 such as a keyboard, a pointing device, a display 24, etc.;one or more devices that enable a user to interact with computersystem/server 12; and/or any devices (e.g., network card, modem, etc.)that enable computer system/server 12 to communicate with one or moreother computing devices. Such communication can occur via Input/Output(I/O) interfaces 22. Still yet, computer system/server 12 cancommunicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 20. As depicted, network adapter 20communicates with the other components of computer system/server 12 viabus 18. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 12. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

Referring now to FIG. 2, illustrative cloud computing environment 50 isdepicted. As shown, cloud computing environment 50 comprises one or morecloud computing nodes 10 with which local computing devices used bycloud consumers, such as, for example, personal digital assistant (PDA)or cellular telephone 54A, desktop computer 54B, laptop computer 54C,digital video camera 54D, digital audio recording device 54E, and/ordigital still camera 54N may communicate. Nodes 10 may communicate withone another. They may be grouped (not shown) physically or virtually, inone or more networks, such as Private, Community, Public, or Hybridclouds as described hereinabove, or a combination thereof. This allowscloud computing environment 50 to offer infrastructure, platforms and/orsoftware as services for which a cloud consumer does not need tomaintain resources on a local computing device. It is understood thatthe types of computing devices 54A-N shown in FIG. 2 are intended to beillustrative only and that computing nodes 10 and cloud computingenvironment 50 can communicate with any type of computerized device overany type of network and/or network addressable connection (e.g., using aweb browser).

Referring now to FIG. 3, a set of functional abstraction layers providedby cloud computing environment 50 (FIG. 2) is shown. It should beunderstood in advance that the components, layers, and functions shownin FIG. 3 are intended to be illustrative only and embodiments are notlimited thereto. As depicted, the following layers and correspondingfunctions are provided:

Hardware and software layer 60 includes hardware and softwarecomponents. Examples of hardware components include mainframes, in oneexample IBM® zSeries® systems; RISC (Reduced Instruction Set Computer)architecture based servers, in one example IBM pSeries® systems; IBMxSeries® systems; IBM BladeCenter® systems; storage devices; networksand networking components. Examples of software components includenetwork application server software, in one example IBM WebSphere®application server software; and database software, in one example IBMDB2® database software. (IBM, zSeries, pSeries, xSeries, BladeCenter,WebSphere, and DB2 are trademarks of International Business MachinesCorporation registered in many jurisdictions worldwide).

Virtualization layer 62 provides an abstraction layer from which thefollowing examples of virtual entities may be provided: virtual servers;virtual storage; virtual networks, including virtual private networks;virtual applications and operating systems; and virtual clients.

In one example, management layer 64 may provide the functions describedbelow. Resource provisioning provides dynamic procurement of computingresources and other resources that are utilized to perform tasks withinthe cloud computing environment. Metering and Pricing provide costtracking as resources are utilized within the cloud computingenvironment, and billing or invoicing for consumption of theseresources. In one example, these resources may comprise applicationsoftware licenses. Security provides identity verification for cloudconsumers and tasks, as well as protection for data and other resources.User portal provides access to the cloud computing environment forconsumers and system administrators. Service level management providescloud computing resource allocation, automation and management such thatrequired service levels are met. Service Level Agreement (SLA) planningand fulfillment provides pre-arrangement for, and procurement of, cloudcomputing resources for which a future requirement is anticipated inaccordance with an SLA.

Workloads layer 66 provides examples of functionality for which thecloud computing environment may be utilized. Examples of workloads andfunctions which may be provided from this layer include: mapping andnavigation; software development and lifecycle management; virtualclassroom education delivery; data analytics processing; and transactionprocessing.

With reference now to FIG. 4, an availability manager 400 of a workloadresource group (WRG) 410 according to an embodiment is shown. Anavailability manager of an embodiment monitors activity running on eachvirtual server 420, 421, 422, 423, 424, 425 on behalf of a WRG 410 anddetermines the availability status of the WRG 410 and its correspondingvirtual servers 420, 421, 422, 423, 424, 425. For example, anavailability status of a virtual server or WRG may be represented as“Available”, “Exposed”, “Critical”, “Not Available”, and “Unreliable.”Each physical server 430, 432, 434 hosts one or more hypervisors 440,442, 444. Each hypervisor hosts one or more virtual servers 420, 421,422, 423, 424, 425. Each virtual server 420, 421, 422, 423, 424, 425represents a share of system hardware resources 450, 452, 454, assupported by each virtualization container, such as CPU, memory, andstorage resources, and hosts separate OS images 460, 461, 462, 463, 464,465. The OS images 460, 461, 462, 463, 464, 465 execute businessapplications, and can be operated and rebooted independently from othervirtual servers. The physical systems 430, 432, 434 are examples ofcompute nodes 10, as shown in FIG. 2 of an embodiment.

Referring to FIG. 5, a flow diagram of a monitoring operation 500 fordetermining the stability of a server based on a stability timespecification of the server according to an embodiment is shown.

In block 510, a stability time is specified for a server. According toan embodiment, the stability time is defined as the time between astarting state of the server and a stability point of the server. Thestability time may be specified during virtual server configuration ormay be determined automatically by the system of an embodiment. Thestability time value may be specified in an external policy orinternally interpreted but displayed in external reports. Automateddetermination of the stability point is accomplished by determining howlong the virtual server remained functional over a historical period oftime. For example, a server that is normally available for long periodsof time would have a higher availability time as it is expected to bestable for longer periods of time. The stability time of an embodimentis used to determine the execution time from the last start or restartof a virtual server until when execution has reached a stability pointto establish that the server is stable and reliable.

Before restarting the server for a subsequent failure, the stabilitytime of an embodiment provides the amount of time that must pass afteran availability manager restarts the server. According to an embodiment,the availability manager does not restart the server if a failure isobserved when the server has executed for less than the stability time.This prevents non-corrected problem from causing repetitive restartthrashing by ensuring that a subsequent restart of a restarted virtualserver after failure will not occur until after the stability time hasexpired. According to another embodiment, the availability manager wouldrestart the server even if the startup time is within the stability timeperiod. However, the instability of the server would be marked in itsavailability status and an overall limit on number of attempts withoutreaching the stability time would be the limiting factor.

According to another embodiment, the stability time may also be used todetermine an abnormal startup time issue, such as a hang or poorperformance during startup. This is determined in response to a startedor restarted server not reaching a stability point within the stabilitytime period. Accordingly, if the initialization of the server is takingtoo long to become available or experiencing a hang situation, anembodiment prevents the server from executing desired workloads due toits instability.

In block 520, the availability manager monitors server activity todetermine the stability and availability status of the server accordingto an embodiment. The availability monitor of an embodiment determinesthe stability of servers by observing whether each server is executingby reaching one or more stability points within the specified stabilitytime for that type of server. In other words, the availability managerobserves each virtual server to determine the time it takes to start theserver to the point that the server is ready to process work. Forexample, virtual servers that are considered stable may have beenprocessing work for a significant period of time (e.g., 30 minutes)before being considered stable. According to an embodiment, theavailability status of each server is selected from a group including anavailable state, exposed state, a critical state, a not available state,and an unreliable state.

According to an embodiment, an agent running in each hosted operatingsystem may further evaluate and represent the execution progress andavailability status of each virtual server, such as when the image isready for work, to the availability manager. For example a web server isnot represented as operating until an HTTP response is received on port80, contrary to contemporary methods that just “ping” the server to seeif it is available. This event is considered the stability point for theweb server according to an embodiment.

In block 530, the availability manager determines whether a stabilitypoint for the observed server has been reached within the specifiedstability time. In response to the server activity progressing to thestability point within the stability time, the availability managerdetermines that the server is stable according to an embodiment, asshown in block 540. In response to the server activity failing toprogress to the stability point within the stability time, theavailability manager determines that the server is unreliable accordingto an embodiment, as shown in block 550.

FIG. 6 depicts a timeline 600 demonstrating the relation between astability time 610, an availability status 620, and a lifecycle of theserver 630 according to an embodiment. The virtual server is activatedvia a programmable request or user request via a user interface. Shortlythereafter, the virtual server enters the starting state. At this pointthe availability manager can start monitoring the progress of thestarted virtual server. Normally, the virtual server environment (i.e.,the virtual machine) will initialize and switch to the operating state.The availability status 620 of the virtual server is designated as “NotAvailable” up to the operating state. However, the OS image has yet tostart. Accordingly, the availability status 620 of the virtual server isdesignated as “Exposed” up until the OS is fully stable. When the OS hasreached a point considered stable enough to process work (i.e., thestability point), the firmware agent signals the availability manageraccordingly and the availability status 620 of the virtual server isdesignated as “Available”.

At some point in the life of the virtual server, the virtual server willeventually be deactivated, for example, to allow for maintenance or tofree orphaned memory. Accordingly, the availability status 620 of thevirtual server is designated as “Not Available” after deactivation.Additionally, FIG. 6 further depicts a situation where the stabilitytime 620 of the virtual server has expired before reaching the stabilitypoint, or has failed and restarted during the stability time interval610. Accordingly, the virtual server in this situation is unreliablebecause the stability point was never reached within the stability time.

Embodiments of the stability time may be used to monitor multiple serverarchitectures across all architectures in the multi-platformenvironment. Additionally, separate stability times may be establishedfor each architecture or virtual server application along with acorresponding stability point. The stability point may be one or moreindicators identified by an agent running in the corresponding OS image.

When focusing on the stability of different types of serverarchitectures, it may be difficult to a choose a single stability timeto prevent restart thrashing, as different server architectures may havedifferent availability characteristics. However, an embodiment providesthe estimation of expected stability times for different types ofworkloads running on specific types of servers. For example, a mainframeserver may be available for days, if not months. Accordingly, anembodiment may set a stability time of one hour because if the mainframefails twice within that time frame, then separate diagnostics andmaintenance may be required.

According to an embodiment, the server may still be restarted if theelapsed time is shorter than the stability time. In that case, however,the server is restarted and marked as “unreliable” to indicate that itwas an exception condition resulting in the server being restartedoutside of the stability time specification to restore availability tothe WRG. Servers in some system architectures may be expected to failfrequently and restarted thereafter. An embodiment addresses thissituation by specifying a lower stability time, such as 30 minutes. Itis possible that the installation considers this manageable byconfiguring a large number of redundant peers in order to keep theoverall function available during times when servers are recycling.Stability time applies to a configured group of redundant servers aswell as dedicated servers in a WRG.

Embodiments disclosed herein provide a stability time and stabilitypoints to an availability manager to monitor the availability of virtualservers executing on multiple servers belonging to differentarchitectures, as well as monitor work executing in a single type ofserver environment. The stability time is used to determine normalavailability characteristics of servers to assist in meeting recoverytime objectives (RTO). Servers that are naturally not stable may beassigned lower stability times, but also require higher levels ofredundancy in order to meet the overall RTO. Accordingly, embodimentsassist in providing guidance to a customer with regard to how muchredundancy would be required. Embodiments can be used by anyavailability manager, whether it is monitoring firmware components,operating system components, automation or the application layer.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described above with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The disclosed flowchart and block diagrams illustrate the architecture,functionality, and operation of possible implementations of systems,methods and computer program products according to various embodimentsof the present invention. In this regard, each block in the flowchart orblock diagrams may represent a module, segment, or portion of code,which comprises one or more executable instructions for implementing thespecified logical function(s). It should also be noted that, in somealternative implementations, the functions noted in the block may occurout of the order noted in the figures. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently, or theblocks may sometimes be executed in the reverse order, depending uponthe functionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of onemore other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated

The flow diagrams depicted herein are just one example. There may bemany variations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

While the preferred embodiment to the invention had been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

What is claimed is:
 1. A computer-implemented method, comprising:specifying, by a processing device, a stability time for a server, thestability time defining a time between a starting state of the serverand a stability point of the server, the stability time being used todetermine availability characteristics of the server to assist inmeeting a recovery time objective, the stability point of the serverincludes when an operating system of the server has reached a pointconsidered stable so that the server can process work; monitoring, by anavailability manager, server activity to determine an availabilitystatus of the server; determining that the server is stable in responseto the server activity progressing to the stability point within thestability time; and determining that the server is unreliable inresponse to the server activity failing to progress to the stabilitypoint within the stability time.
 2. The computer-implemented method ofclaim 1, wherein the server is marked as unreliable in response to theserver being restarted prior to progressing to the stability point. 3.The computer-implemented method of claim 1, wherein the availabilitymanager prevents the server from restarting until the stability time hasexpired to prevent thrashing.
 4. The computer-implemented method ofclaim 1, further comprising an agent of the server, the agent evaluatingand reporting the server activity to the availability manager.
 5. Thecomputer-implemented method of claim 1, wherein the stability time isspecified during server configuration and is based on a determination ofserver functionality over a historical period of time.
 6. Thecomputer-implemented method of claim 1, wherein the availability statusof the server is selected from a group comprising an available state, anexposed state, a critical state, a not available state, and anunreliable state.
 7. The computer-implemented method of claim 6, whereinthe exposed state is defined as a time between an operating state of theserver to the stability point of the server.
 8. A computer programproduct, comprising: a non-transitory computer readable storage mediumhaving computer readable program code stored thereon that, when executedby a processing device, causes the by the processing device to performoperations comprising: specifying a stability time for a server, thestability time defining a time between a starting state of the serverand a stability point of the server, the stability time being used todetermine availability characteristics of the server to assist inmeeting a recovery time objective, the stability point of the serverincludes when an operating system of the server has reached a pointconsidered stable so that the server can process work; monitoring, by anavailability manager of the processing device, server activity todetermine an availability status of the server; determining that theserver is stable in response to the server activity progressing to thestability point within the stability time; and determining that theserver is unreliable in response to the server activity failing toprogress to the stability point within the stability time.
 9. Thecomputer program product of claim 8, wherein the server is marked asunreliable in response to the server being restarted prior toprogressing to the stability point.
 10. The computer program product ofclaim 8, wherein the availability manager prevents the server fromrestarting until the stability time has expired to prevent thrashing.11. The computer program product of claim 8, further comprising an agentof the server, the agent evaluating and reporting the server activity tothe availability manager.
 12. The computer program product of claim 8,wherein the stability time is specified during server configuration andis based on a determination of server functionality over a historicalperiod of time.
 13. The computer program product of claim 8, wherein theavailability status of the server is selected from a group comprising anavailable state, an exposed state, a critical state, a not availablestate, and an unreliable state.
 14. The computer program product ofclaim 13, wherein the exposed state is defined as a time between anoperating state of the server to the stability point of the server.